Olefin based polymers such as polyethylene are produced via various catalyst systems and polymerization processes. Selection of such catalyst systems used in the polymerization process of the olefin based polymers is an important factor contributing to the characteristics and properties of such olefin based polymers.
The polyolefin polymerization process can be varied in a number of ways to produce a wide variety of resultant polyolefin resins having different physical properties suitable for use in different applications. It is generally known that polyolefin can be produced in a solution phase polymerization process, gas phase polymerization process, and/or slurry phase polymerization process in one or more reactors, for example, connected in series or parallel, in the presence of one or more catalyst systems. The use of activating agents in polyolefin polymerization process to activate the pre-catalyst composition is generally known. Certain pre-catalysts, for example, require an activating agent such as dihydrogen to become catalytically activate for olefin polymerization. For example, dihydrogen has been shown to activate bis(trimethylsilyl)methyl scandium pre-catalyst (Catalyst 1). However, the presence of dihydrogen also leads to termination of the growing polymer chains via σ-bond metathesis with metal-polymer bonds, and as a result a decrease in polymer molecular weight is observed.

Accordingly, there is a need for a catalyst composition suitable for polymerization process in the absence of activators, e.g. dihydrogen.